Spatial hearing abilities in adults with bilateral cochlear implants. Smita Satish Agrawal

ISBN: 9780549804093


NOOKstudy eTextbook

136 pages


Spatial hearing abilities in adults with bilateral cochlear implants.  by  Smita Satish Agrawal

Spatial hearing abilities in adults with bilateral cochlear implants. by Smita Satish Agrawal
| NOOKstudy eTextbook | PDF, EPUB, FB2, DjVu, AUDIO, mp3, RTF | 136 pages | ISBN: 9780549804093 | 6.74 Mb

An increasing number of persons with severe to profound hearing loss are opting for bilateral cochlear implants (BiCI) in an attempt to access the benefits offered by listening through both ears. Numerous studies have demonstrated that two implants are better than one for localizing sound sources in quiet, controlled acoustic environments. However, complex listening environments continue to pose difficulties for BiCI listeners. The present series of experiments compared measures obtained in free-field (FF) using uncoordinated clinical speech processors with measures obtained using direct electrical stimulation (DS) with a research processor.

First, the ability to localize sounds was studied in these simulated realistic listening conditions: (1) in the presence of interfering sounds, (2) with target uncertainty and (3) dual-tasking for sound localization and speech identification. Second, localization performance in FF was compared with binaural sensitivity to interaural time difference (ITD) and interaural level difference (ILD) cues measured using DS. Finally, the extent to which directional information in echoes can be suppressed, i.e., the phenomenon of the precedence effect (PE) was evaluated in FF and under DS.-Results showed that sound localization ability in listeners with BiCI is significantly affected by the presence of interferers.

Localization ability in FF was significantly correlated with the ITD sensitivity under DS suggesting that listeners who are best able to localize sounds in FF also are best able to make use of ITD cues available when performing DS tasks. BiCI listeners demonstrated PE that was similar to that reported in listeners with NH when stimulated under DS suggesting that the auditory system of BiCI listeners has the necessary mechanisms to elicit important binaural effects such as echo suppression. PE was also observed when listening via clinical processors- however the effect was weak.

Possible reasons for degraded performance in FF include limited binaural cues, especially ITDs, provided by the clinical speech processors, a lack of co-ordination in input across the two ears and temporal smearing caused by the clinical processors. Improvement in speech processors and/or microphone algorithms may be required to produce better results in everyday acoustic environments.

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